Camera modules designed to capture images of objects that emit near-infrared (near-IR) light are used in applications such as gesture detection, head and eye tracking, and motion detection. For example, FIG. 1 depicts a hand 190 in the field of view of a gesture recognition system 110. A camera module 120 images hand 190, which moves in directions x, y, and z of a coordinate system 198. Camera module 120 includes an image sensor 130 and an imaging lens 100. Image sensor 130 includes a pixel array 132 upon which imaging lens 100 forms an image of hand 190. Pixel array 132 has a width 132W and imaging lens 100 has an optical axis 100X.
Effectiveness of gesture recognition system 110 depends on its ability to meet performance specifications at a temperature range characteristic of its application. For example, a typical temperature range for automotive applications is −40° C. to 125° C. Hence, the accuracy of gesture recognition depends in part on imaging lens 100's being athermalized such that it forms a clear image on image sensor 132 within the temperature range associated with its application. For example, lens 100 images light 192 propagating from a point 190P on hand 190 to a point 102. Light 192 is for example near-IR light. Point 102 is located a field height x1 from optical axis 100X and a focal shift Δz1 from pixel array 132. Focal shift Δz1=0 corresponds to when imaging lens 100 forms an in-focus image of point 190P on image sensor 132. The magnitude of focal shift Δz1 as a function of field height x1 and ambient temperature T is an athermalization metric for lens 100.